Java message service framework in the Java library usage guide
The Java Message Service Framework (JMS) is a message transmission specification implemented in the Java class library.It allows applications to exchange information asynchronously through message queues or themes, providing a flexible and reliable solution for constructing distributed applications.This article will introduce the guidelines for the Java message service framework and provide some Java code examples.
** 1. Understand the core concept of JMS **
Before using JMS, we need to understand some of the core concepts:
- "Producer": Responsible for creating and sending messages to message queues or themes.
- "Consumer": Responsible for receiving and processing messages from the message queue or theme.
- "message queue" (queue): a mechanism that stores messages in accordance with FIFO, and the message can only be accepted by one consumer.
-"Topic": a mechanism for storing messages to storage by Publish-Subscribe, and messages can be accepted by multiple consumers.
- "ConnectionFactory": Factory objects used to create JMS connection.
-"Connection": connect to the network connection established with the message agent for sending and receiving messages.
- "Session": The context created by connecting to the context environment for sending and receiving messages.
-"Destination": The goal of message sending and receiving can be the message queue or theme.
** 2. Basic steps of JMS **
The following are the basic steps to write applications using the JMS framework:
** Step 1: Create a connection factory **
ConnectionFactory connectionFactory = new ActiveMQConnectionFactory(brokerUrl);
The ActiveMQConnectionFactory is used here as an instance that connects the factory. Brokerurl is the URL address of the message proxy.
** Step 2: Create a connection **
Connection connection = connectionFactory.createConnection();
Create a connection by connecting the factory.
** Step 3: Start the connection **
connection.start();
The connection needs to be activated to start sending and receiving messages.
** Step 4: Create the meeting **
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
By connecting to the creation, the first parameter represents whether it enables transactions, and the second parameter represents the message confirmation mode.
** Step 5: Create a destination **
Destination destination = session.createQueue("myQueue");
Create a message queue or theme as needed.
** Step 6: Create producers or consumers **
MessageProducer producer = session.createProducer(destination);
Create producers or consumers through session and destinations.
** Step 7: Send or receive message **
TextMessage message = session.createTextMessage("Hello JMS!");
producer.send(message);
Use producers to send messages to the destination.
MessageConsumer consumer = session.createConsumer(destination);
Message message = consumer.receive();
if (message instanceof TextMessage) {
TextMessage textMessage = (TextMessage) message;
System.out.println("Received message: " + textMessage.getText());
}
Use consumers to receive and process messages.
** Step 8: Close the connection **
connection.close();
At the end of the program, close the connection to release resources.
** 3. Specific example **
The following is a simple example that demonstrates how to send and receive messages using JMS:
import org.apache.activemq.ActiveMQConnectionFactory;
import javax.jms.*;
public class JmsExample {
public static void main(String[] args) throws JMSException {
String brokerUrl = "tcp://localhost:61616";
ConnectionFactory connectionFactory = new ActiveMQConnectionFactory(brokerUrl);
Connection connection = connectionFactory.createConnection();
connection.start();
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
Destination destination = session.createQueue("myQueue");
MessageProducer producer = session.createProducer(destination);
TextMessage message = session.createTextMessage("Hello JMS!");
producer.send(message);
System.out.println("Message sent: " + message.getText());
MessageConsumer consumer = session.createConsumer(destination);
Message receivedMessage = consumer.receive();
if (receivedMessage instanceof TextMessage) {
TextMessage textMessage = (TextMessage) receivedMessage;
System.out.println("Message received: " + textMessage.getText());
}
connection.close();
}
}
Through the above examples, we can send a message from the message queue and receive the message from the same queue.
**Summarize**
This article introduces the JAVA Message Service Framework (JMS) in the Java class library, including core concepts, basic steps, and example code.Through JMS, we can build a reliable distributed application to achieve asynchronous news transmission.I hope this article can help readers better understand and use the JMS framework.
